Early-stage research suggests e-cigarettes may have closer ties to cancer than we thought.

E-cigarette vapor causes lung cancer and potentially bladder cancer in mice, damaging their DNA and leading researchers at New York University to conclude that vaping is likely “very harmful” to humans as well.

In this experiment, lead study author Moon-Shong Tang, Ph.D., a professor at New York University’s Department of Environmental Medicine, and a team of scientists investigated what happens to mice exposed to two types of vapor: nicotine-laden vapor from a e-cigarette and a vapor that contained two additives used in e-juice: propylene glycol (PG) and vegetable glycerin (VG), but no nicotine. Then, they compared those mice to a control group.

These mice were literally surrounded by vapor for four hours per day for five days each week. This isn’t how a person would use an e-cigarette, which is an issue that this team has been criticized for in the past.

By the time the experiment ended, nine of the 40 mice (22.5 percent) exposed to typical e-cigarette vapor developed lung cancer, while only one of the mice in either control group did the same. More than half of the e-cigarette vapor group also developed an enlarged bladder (a condition called hyperplasia), a risk factor for bladder cancer, compared to a single mouse who did the same across both control groups.

There were limitations to the study. The mice did not inhale the vapor as deeply as a human would, for instance. It also was conducted in a small number of mice that were more likely to develop cancer over their lifetime, researchers noted.

Other scientists have found the presence of chemicals known to be carcinogenic in e-cigarette vapor, especially from flavored products. But the new study, published in the journal PNAS, is perhaps the first to so directly tie e-cigarettes to cancer.

A February study by the University of Southern California also found that e-cigarette users developed some of the same molecular changes in oral tissue that cause cancer in cigarette smokers, according to the study published in the International Journal of Molecular Sciences.


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